Pass variable file path to batch file?

I need some help passing a variable to a batch file, specifically the path of a file. My batch file looks something like this:
net use lpt2: serverdesignjet
copy /b filename.plt lpt2
net use lpt2: /delete

It would be great if users could just drag a .plt on to this batch file and have it run. Currently the have to move the .plt file and rename it, which as you can imagine isn't very fast.

Although it does appear that some users attempt to paste the line numbers with the code. You can do it by starting the drag at the numbers. One user insisted it was a bug and asked if I would repost the code in a message.